1. Field of the Invention
This invention relates to automatic cable wrapping equipment and, more particularly, to cable wrapping equipment in which a spindle assembly carrying the wrapping material moves along the length of the cable as the cable is being wrapped.
2. Prior Art
Winding of magnet structures with super-conducting conductors, or cables, has heretofore required preliminary preparation of the superconductor cable prior to the actual magnet winding operation. The superconductive material is wrapped in a helical pattern with one or more tapes of thin plastic insulating material, such as that provided under the tradenames Mylar or Kapton. The wrapped, insulated cable is then stored on reels until needed for use with a magnet winding machine. One disadvantage of this method is that the bare cable and the wrapped cable are handled several times prior to actual winding of a magnet which increases opportunities for damage to either the cable or to the wrapped cable. Scuffing and entrapment of metal chips might cause short circuits between the turns of a coil wound with the cable. Entrapment of dirt changes the dielectric characteristic of the cable.
One prior art method of winding super-conductive cable with insulating tapes involves drawing the cable through a modified lathe using a capstan driven by a lead screw connected to the lathe gear train. Spools of insulating tape are mounted on a winding head which replaces the conventional lathe chuck. The rotation of the winding head and the turning of the capstan are controlled by the lathe gear train. The capstan allows the cable to slip. This method works with continuous feeding of cable, but is not suitable for intermittent winding functions, such as required for "on demand" operation in which the cable is wrapped just before being wound into a magnet structure. During the frequent stopping and starting required by this type of operation, the inertia of the lathe gear train and the chuck drive causes tangling and jamming of the tape, even though a detector may be provided which senses that the cable is being twisted and turns off the drive motor and applies a brake.
A number of machines are known in the prior art which use a head, or spindle, rotating around the conductor, for winding insulating tapes around a conductor. Almost all of these prior art techniques fix the position of the rotating spindle such that it remains stationary with respect to the cable moving through a machine from a supply reel to a takeup reel. An example of this type of machine is shown in U.S. Pat. No. 1,204,342, granted Nov. 7, 1916.
Some prior art tape winding machines have spindles which travel along the length of a cable being wrapped. U.S. Pat. No. 4,249,704 granted Feb. 10, 1981 shows a machine for automatically winding a fixed object such as a curved bus bar or the like. A rotating spindle is moved along the length of the object to be taped under control of a digital computer, in which is stored the cooordinates of a multiplicity of points describing the central axis of the object. This machine requires entry and storage of the coordinates for the object to be taped and uses previously stored information, rather than the object itself, to guide and control the winding spindle. The object to be wound is stationary and no provisions are made for movement or displacement of the object being wound, such as would be produced, for example, during the actual winding of a magnet structure. No provisions are made for the horizontal and vertical movement of a cable as a magnet is being wound with a cable fed from a supply reel or the like.
U.S. Pat. No. 3,940,073 granted Feb. 24, 1976 discloses apparatus for wrapping compound-curved conductor bars. The winding head carries sensors for measuring the change of position of the winding head with respect to the conductor bar. Correctional signals proportional to the relative position between the winding head and the conductor bar are provided to maintain the winding head perpendicular to the center line of the conductor bar.